Devices and methods for in flight transition vtol/fixed wing hybrid aircraft structures and flight modes

ABSTRACT

A hybrid VTOL/high speed aircraft may comprise systems and functions for in flight configuration changes from high lift helicopter or VTOL mode to fixed or swing-wing high speed aircraft mode to accommodate a variety of functions or missions.

FIELD OF THE INVENTION

Embodiments relate to hybrid VTOL (helicopter)/Fixed or Swing WingAircraft devices and corresponding methods. More particularly,embodiments relate to hybrid aircraft that combine and transition inflight from and to a low speed/high lift vertical takeoff or landing(VTOL) helicopter configuration to a high speed/low drag fixed or swingwing jet or propeller driven aircraft configuration in order to takeadvantage of the characteristics of each configuration in a single craftfor different mission phases of flight. Embodiments may be configuredfor manned or unmanned (drone) applications, and may also be configuredfor heavy lift/medium to high speed transport or light lift/high speedfunctions or any combination of these configurations. Other embodimentsmay relate to methods and devices for helicopter configurations ofsingle or coaxial counter-rotating rotor blade sets as the VTOLcomponent of such hybrid aircraft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a hybrid aircraft, according to one embodiment;

FIGS. 2A, 2B, and 2C illustrate various views of a twin rotor blade setand rotor hub, according to one embodiment;

FIG. 3A is a side view of two coaxial counter-rotating rotor hubs andblades, and FIG. 3B is a top view of a two pair of coaxialcounter-rotating blade sets, according to embodiments;

FIG. 4 is a top view of a hybrid aircraft with wings and rotors folded,according to one embodiment;

FIG. 5 is a top view of a hybrid aircraft in one phase of a flight mode,according to one embodiment;

FIG. 6 is a top view of a hybrid aircraft in one phase of a flight mode,according to one embodiment;

FIG. 7 is a top view of a hybrid aircraft in one phase of a flight mode,according to one embodiment;

FIG. 8 is a top view of a hybrid aircraft in one phase of a flight mode,according to one embodiment;

FIG. 9 is a top view of a hybrid aircraft in a transitional phasebetween flight modes, according to one embodiment;

FIG. 10 is a rear perspective view of the empennage of a hybridaircraft, according to one embodiment;

FIG. 11 is a top perspective view of cockpit controls and layout of ahybrid aircraft, according to one embodiment.

DETAILED DESCRIPTION

Reference will now be made In detail to the construction and operationof embodiments illustrated in the accompanying drawings. The followingdescription is only exemplary of the embodiments described and shownherein. The embodiments, therefore, are not him ted to theseimplementations, but may be realized b other implementations.

Embodiments are drawn to high lift (VTOL)/high speed hybrid aircraftdevices and methods that combine the capabilities of a helicopter withthose of fixed of swing wing, aircraft. Embodiments may comprisemethods, structures and functionality for composite or mixed controlsystems, single or coaxial counter-rotating, rotor blade sets, fixed orswing wing aircraft structures, increased directional control optionsand sensitivity and in flight helicopter to fixed or swing wingconfiguration changes to allow for maximum mission efficiency.Embodiments may be electrically, mechanically, hydraulically and/ormanually controlled, powered and operated, and may be operated as manned(direct control) or unmanned (remotely controlled) or bothconfigurations platforms

A hybrid, aircraft device, according to embodiments herein, may be usedto advantage to fulfill the roles of both an efficient. VTOL aircraftand an efficient high speed aircraft during selected mission phases.According to embodiments, described, herein are methods of changingin-flight configurations from one form of flight, such as VTOL, toanother form of flight, such as high speed fixed or variable swing wingoperations. Traditionally, the limiting factors for maximum speed,approximately 150 knots, of a conventional helicopter design includesuch concepts as numbers of rotor blades per set, rotor blade profile,aspect ratio, chord thickness, stiffness, tip speed, retreating bladestall factors, dissymmetry of lift, airflow reversal and dissymmetricaldrag, as well as both profile and induced drag on the spinning rotorblade set(s). Indeed, Rotor blade design is often based on a compromisebetween lift efficiency in hovering or vertical flight and drag andpropulsion factors in forward flight. Rotor tip speed for an advancingrotor blade may approach the speed of sound, at which point dragincreases even more rapidly than as a cube function of rotor speed.Retreating blade speed through an air mass is directly related toforward speed of a conventional helicopter, and both stalling, speedconditions and airflow reversal over the retreating rotor blade mayresult in extreme dissymmetry of lift and/or cause pitch changes in theaircraft, and are the major limiting factors on conventional helicopterspeed. Even with coaxial, counter-rotating blade sets as the primarylift structure coupled with auxiliary thrust mechanisms, recentlydemonstrated to exceed 250 knots, the increasing, drag on the twin rotordiscs at higher speeds ultimately limits the maximum speed limit of suchadvanced aircraft. Moreover, vibration must be strictly controlled tomaintain stable flight at such speeds.

Embodiments overcome these limitations through hybrid design factors asdescribed herein, which thus allow in-flight configuration changes ormodes for maximum efficiency in both VTOL operations and for forwardflight speed. According to one embodiment, during forward high-speedflight, the rotor blade sets may be feathered to a stored position onthe airframe, and are not relied upon to provide the lift. Thesefeathered and stored rotor blade sets are, according to one embodiment,not necessary for the high-speed phase of flight and thus do not presentthe disadvantages associated with conventional helicopters, such as thelimitations on speed. Moreover, according to embodiments described,herein, the ability to change aircraft configurations during a flightprofile from a VTOL configuration to a high speed fixed or swing wingconfiguration and vice versa presents advantages such as choice oftakeoff or landing sites, fuel conservation, longer maximum flightdistances or legs, quietness, increased safety factors and moreflexibility of flight profiles for various missions.

Herein, the term “fixed wing” may be used to contrast a high speedconventional aircraft structure and mode of flight operations to that ofa helicopter or VTOL flight mode, as is commonly used to distinguishbetween the two aircraft types. The term fixed wing as used for thishybrid aircraft, according to embodiments, encompasses embodiments inwhich fixed stub wings are permanently affixed to the fuselage, as wellas embodiments in which the wings may be swing-wings. Such swing-wingsmay be active in different flight profiles, i.e., further extended forslow speed flight and swept or partially retracted for high speedflight, or completely stowed for helicopter or VTOL flight modes, toallow efficient downwash or air mass movement from the rotor discs.According to one embodiment, both the rotor blade sets and swing-wingsof a hybrid aircraft as shown and described herein may be folded toallow storage in tight spaces such as on a flight deck or in a hangar,or for efficient transport b aircraft, carriers, rail systems or othermeans.

Reference will now be made in detail to the structure and operation ofembodiments illustrated in the accompanying drawings. FIG. 1 shows aside view of a hybrid aircraft 10 having a generic fuselage 8 andcoaxial, counter-rotating rotor blades 14 and 16 and folded swing-wings34, according to one embodiment. This view also shows external featuressuch as retractable landing gear 30 and 32, twin direct jet propulsionunits 26 with alternate gated 130 power turbine modules 24, rear entryport 25, tail-hook 28, rear empennage including twin rudders 18 andhorizontal stabilizers 20 and associated control surfaces, and “No TailRotor” (NOTAR) bleed air gas ports 22. At the top of the fuselage, afairing 11 to streamline the stowed rotor hubs 12 (13 not, shown in thisview) in lowered position may also be noted. Such a fairing 11 may bemovable vertically or otherwise to unmask the rotor blades 14, 16 whendeploying them or for streamlining the fuselage frontal area when therotor blades 14, 16 are folded and stowed. Although not shown in thisview, a canard wing may be incorporated into the forward section of thefuselage to provide increased lift, stability and pitch control,according to another embodiment. A pair of leading edge root extensions(LERX) 90 may add additional lift in near stall conditions and provideadditional structural stability and streamlining to the swing-wings 34.

According to other embodiments, the main direct propulsion single ortwin jet unit(s) may be separate from additional single or twin jetrotor transmission power units. According to still other embodiments,either or both main or rotor engine units may be piston driven, and maybe combined or separate in terms of propulsion purpose. In still otherembodiments, a main fixed wing mode thrust may be accomplished by theuse of piston engines, or turboprop engines with fixed pitch or constantspeed, full feathering propeller(s), which may be counter-rotating. Itis to be understood that any combination or configuration of any of theforegoing is to be considered as being within the scope of thisdisclosure, as will be apparent to one skilled in the art. The rotorblade sets 14 and 16 are shown folded and stowed along the long axis ofthe fuselage 8 in this low wing configuration. However, according to oneembodiment, with the main fixed (swing) wings 34 in a high wingconfiguration, stowage of the partially folded rotor blades along, orwithin the upper surface of such high wings may be envisioned.

According to embodiments, various fuselage profiles, rotor profiles,NOTAR or tail rotor, wing profiles and other features discussed hereinmay he incorporated into a hybrid aircraft, as one skilled in the an mayenvision. Element 31 represents an approximate center of gravity for thegeneric fuselage 8, as illustrated. Advantageously, the center ofgravity for both VTOL and fixed wing flight configurations may bedesigned to fall within a narrow sphere within the fuselage. Althoughthe center of gravity position as shown in this illustration isrelatively low for a helicopter, the long arm pendulum effect increasesstability of the aircraft in VTOL mode which may be advantageous intransitioning from one flight mode to another in flight, according toembodiments. The fuselage 8 may be of any morphology or dimensions, andthe illustration shown is conceptual in nature for purposes ofdiscussion herein and is not intended as limiting the scope of theembodiments shown and described herein.

FIGS. 2A 2B and 2C illustrate various views of a twin rotor blade setand rotor hub, according to one embodiment. FIG. 2A illustrates a topdown view of a composite rotor hub 12 with one blade root attachment 14Ato one (outer, in this illustration) driven portion 12A of the rotor hub12 and a second, foldable or feather-able, non-driven blade root 14Baffixed to a second (inner, in this illustration) non-driven portion1213 of the main two part rotor hub 12. As used herein, the term“driven” for a portion of the rotor hub refers to the fact that suchportion is driven in rotation by direct coupling to the driveshaft forthat rotor hub, and the “non-driven portion” of the rotor hub refers tothe fact that such portion is not driven by direct coupling, to thedriveshaft, but is actually driven by the driven portion of the rotorhub when it is engaged in a certain position relative to the drivenportion of the rotor hub. According to embodiments, a rotor hub mayconsist of one driven portion and any number of non-driven portions. Itis assumed that the direction of rotation of the rotor hub 12 iscounterclockwise as shown by the arrow. According to one embodiment,where coaxial, counter-rotating rotors are used, a mirror image of thecomposite hub of FIG. 2A with rotation in a clockwise direction (lowerof the two rotor hubs), may be envisioned. The inner non-driven portion1213 of the rotor hub 12, represented by the dashed lines, according toone embodiment, is allowed to move freely inside the outer drivenportion 12A with a limited radius of travel, as shown by the solid stoppositions illustrated by the internal solid half circle attached to theblade root 14A. In this manner, the fully extended rotor blade roots 14Aand 14B are illustrated in this figure, and the feathered or foldedblade roots 14A and 14B may be seen in FIG. 2C.

As shown in FIG. 2B, the vertical driving shaft 50 of the rotor hub 12,coming from the hub transmission (not shown in this view), is fixed toand acts directly on the driven portion 12A of the rotor hub, allowingthe non-driven portion 1213 to rotate freely, and that the non-drivenportion 12B of the rotor hub 12 will in turn drive the non-driven rotorblade 14A when the maximum relational travel between the driven ormaster hub and non-driven hub portions has been reached. It may be notedthat the assembly process for the composite rotor is simply a matter ofsliding the two main driven and non-driven portions 12A and 1213together and sliding the rotor driving shaft up to positive engagementand locking to the driven portion 12A. The relationship between the twoblades is that they may be fully deployed opposite to each other orfeathered with the blades lying in close proximity to one another.Although in these illustrations, two blades are affixed to the rotor hubsystem, any number of blades may be affixed, with one of the blades 14Afixed to the driven portion of the rotor hub system and with additionalblades configured as non-driven, according to additional embodiments.

FIG. 2A also illustrates a spring-loaded solenoid lock 46, representedby a blackened circle in this illustration, which may be permanentlyaffixed to driven portion 12A. The solenoid lock 46 serves to lock theblades and hub portions together when the blades are opposite to eachother, i.e., in a fully deployed position and again when the blades arefully feathered as in FIG. 3C, again represented by a blackened circlebut in a different place relative to the non-driven portion I 2B of therotor hub 12. The open circles represent alternate positions in whichthe solenoid 46 may be engaged. The spring-loaded solenoid 46 may alsobe seen in FIG. 2B, and the placement of the spring implies that thepiston of the solenoid is normally engaged against the non-drivenportion 12B. In this manner when it is desired to either deploy orfeather the blades, activating the solenoid 46 releases or unlocks thehub non-driven portion 12B from driven portion 12A, and when the bladesreach the position desired, the piston of the solenoid 46 willautomatically engage the appropriate locking hole in hub non-drivenportion 12B. The solenoid 46 may also feature a brake pad affixed to itsvertical tip, which may act to control or slow the rotation of oneportion of the rotor hub in relation to the other portion.

It should be noted that in this disclosure, the term “feathered” impliesthat the blades are disposed one at least partially over another infolded position, as opposed to the use of the term to imply that theleading edge of the blade is facing the relative wind, such as used todescribe feathering propellers to reduce drag. Blade pitch control rodsor pitch links attached to the leading and trailing blade root edgesconnect to an upper swashplate, which is controlled via a lowerswashplate by inputs from the collective and pitch or joystick controls,such as found in conventional helicopter designs. Other features, suchas scissors links, counterweights, lead-lag vertical hinge pins, detailsof blade grips, flapping hinges, blade shock absorbers, Arthur Youngstabilizer bars (flybars) and other features are not illustrated in FIG.2A for the sake of simplicity, but such features may he incorporatedinto the rotor hub/blade design, according to embodiments. Additionally,rotor blades themselves may incorporate any number or combination offeatures, such as twist and taper profiles, aspect ratios, varying chordthicknesses, root cutouts, rigidity or semi-rigid designs, or otherfeatures, according to embodiments. According to embodiments, the rotorroots 14A and 148 may be half round segments to allow them to fully nesttogether, even beyond the close approximation shown in FIG. 2C,particularly if blade root cutouts are incorporated next to the rotorhub 12.

FIG. 2B is a representative side view of a composite hub structure 12 inmore detail, according to one embodiment. The drawing is notspecifically to scale. Herein, the use of the term “composite” impliesthat the hub system may comprise more than one single monolithic centralhub structure with attachments for the rotor blades and the like, and isnot intended to connote the material or materials of which the hubsystem may be made. At the top of this illustration, the composite rotorhub 12 may be seen with its driven portion 12A and the non-drivenportion 12B with counterweights 54, the spring-loaded solenoid lockmechanism 46 and the rotor roots 14A and 14B. Lever arms 60 and 62 arefixed to and swivel about the rotor roots 14A and 14B for pitch changesto the rotor blades. The counterweights 54 balance the non-drivenportion in relation to the driven portion of the hub. The non-drivenportion may have less mass than the driven portion in order to fitbetween the upper and lower sections of the driven portion. Thecounterweights 54 ensure that equal weight between the driven portionand the non-driven portion. The rotor blade roots are where it isessential to have balance, like on a drive shaft, to avoid unwantedinduced vibration. The driveshaft 50 of the mast, which rotates with therotor hub 12, is surrounded by the non-rotating outer mast housing 52,to which are affixed servos 48 that receive collective and cycliccommands from the controls and act on the lower swashplate 42. Suchservos 48 may be two or more in number and may be arranged as a Stewartplatform with three servos. The upper swashplate 40, like the compositerotor hub 12, may comprise corresponding sliding segments 40A and 40B,which allow the upper rotating swashplate 40 to feather with the rotorblades 14A, 14B, mimicking the rotor hub 12 as shown in FIGS. 2A and 2C.Pitch links 56 are attached to the lever arms 60 and 62 to inputcollective and cyclic command movements to the driven blade 14A and tothe non-driven blade 14B. According to one embodiment, when the upperswashplate 40 is in feathered position, the pitch links 56 nest in closeproximity to one another. Scissor links such as shown at 44 allowmovement of the upper swashplate 40 while ensuring, that rotation of theupper swashplate portion 40A is, at all times, synchronous with therotor hub driven portion 12A. According to another embodiment, theservos 48 may be positioned on the outer mast sheath 52 between therotor hub 12 and upper swashplate 40 inside the pitch links. In thatcase, the servos 48 would act on the lower swashplate 42 by pullingthereon from above instead of pushing it upward from below, or may bearranged in an upside down Stewart platform. Such a configuration mayresult in a more compact rotor head assembly, which may also allowcloser stacking of a coaxial counter-rotating rotor hub assembly pair.According to another embodiment, the servos 48 may replace and act asthe pitch links 56 themselves and may be located respectively andattached to the driven and non-driven portions of the rotor hub, withone servo per rotor hub portion and configured with control inputs suchas electronic signals and power sources incorporated into the rotatingdriveshaft itself for a given rotor hub. Each servo would thereforecontrol rotor blade pitch by direct attachment to its respective rotorblade lever arm 60 or 62. In such an embodiment, the use of such directservos may obviate the need for a swashplate altogether, and since eachservo is attached to its respective rotor hub portion, they may benestled in close proximity together when the rotor hub is in its foldedor feathered position, as discussed above for the pitch links 56. Fly-bywire systems may, according to one embodiment, be used to controlindividual blade pitch, and such fly-by-wire systems are assumed to beincorporated into further discussions of embodiments of a hybridaircraft below.

FIG. 2C is a top view of a rotor hub 12, with the rotor roots 14A and14B in a feathered configuration in which they nearly overlap eachother. It is assumed that if the aircraft were hung underneath the rotorhubs illustrated in FIGS. 2A and 2C with the forward part of thefuselage pointing to the top of the page, and if the rotor hub 12 ofFIG. 2A were stopped in that position, then airflow from forward flightof the aircraft would allow both roots and blades 14A and 14B to fallback and align themselves aft of the rotor hub 12 to the position shownin FIG. 2C.

FIG. 3A is a side view of two coaxial counter-rotating rotor hubs andblades, and FIG. 3B is a top view of a pair of coaxial counter-rotatingblade sets, according to embodiments. In FIG. 3A, the upper rotorhub/blade set includes the driven portion 12A of the rotor hub 12 andthe non-driven portion 12B of the rotor hub, as has been previouslyillustrated. Not shown are details such as the corresponding upperswashplate and other details from FIG. 2B above, but which are assumedto be present. In this figure, a lower rotor hub/blade assembly 13 withdriven rotor hub 13A and non-driven rotor hub portion 13B areillustrated, and are essentially mirror structures of the upper rotorhub/blade assembly, designed to rotate in a counter direction to theupper rotor hub/blade set. Driven blade 16A, therefore, is illustratedshowing its trailing edge and non-driven rotor blade 16B presents itsleading edge. It is assumed that the upper blade set, with driven blade14A showing its trailing edge, and non-driven blade 14B, showing itsleading edge in this illustration, rotates in a counter-clockwisedirection viewed from above, and therefore the lower blade set willrotate in a clockwise direction, as shown in FIG. 3B. FIG. 3A also showsfour concentric tubular sections of the rotor mast, including, from theinnermost out, the rotating upper hub drive shaft 50; the non-rotatingupper hub mast sheath 52 supporting and controlling the lower swashplateassociated with the upper rotor hub 12; the rotating lower rotor hub 13drive shaft 64; and the non-rotating lower hub outer mast sheath 66,with analogous functions to sheath 52. According to one embodiment, theupper rotor mast sheath 52 and lower rotor mast sheath 66 mayincorporate streamlining shapes below their respective rotor hubs foraerodynamic efficiency and drag reduction purposes since both mastsheathes are non-rotating in relation to the fuselage 8 of a hybridaircraft 10 of FIG. 1 above. The gears illustrated on drive shafts 50and 64 are drawn to imply counter-rotation of the two shafts in relationto each other. There are many gear/belt arrangements possible forapplication to a coaxial counter-rotating helicopter transmission, thehousing of which is shown as element 70 in this illustration, and sucharrangements are well known in the art and are not discussed herein.Embodiments may incorporate any or all of such arrangements, as would beenvisioned by on skilled in the art. According to embodiments, anauxiliary electric, or hydraulic drive motor or motors (not shown inthis illustration, but easily envisioned) may be added to the main rotortransmission/clutch drive mechanism (not shown, as described above) firlow speed rotation of the rotor hubs through the gears of drive shafts50 and 64 for purposes such as rotating the rotor hubs to deploy or foldthe rotor blades for maintenance, stowage, or in addition for deployingthe rotor blades from feathered configuration to deployed configurationin preparation for autorotation functions, for example in the event ofmain engine failure in a hybrid aircraft's fixed wing flight mode. Theauxiliary motor(s) may also be used to move, augment and positivelycontrol rotor blade positions relative to the fuselage during in-flighttransition modes from VTOL to fixed wing configurations and vice versa.Also not shown, but easily envisioned may be a clutch/disc brakeassembly affixed to the drive shafts 50 and 64 for purposes ofdecoupling the drive shafts from the main transmission and braking theirrotation. The disc brakes may be horizontally affixed to the driveShafts, and the disc pad assemblies located on their respectivenon-rotating mast sheathes 52 and 66.

In addition to the elements or components described above, a hydraulic,or mechanical scissor link 68 or links or other mechanism may be used toraise or lower the rotor hub(s) in relation to each other, which may beadvantageous in reducing the moment inherent in vertically-stackedcoaxial counter-rotating rotor blade sets, and/or to the fuselage 8 of ahybrid aircraft 10. This may be advantageous in stowing the rotor bladesets in their folded or feathered configuration, thus streamlining theaircraft if operating in fixed wing mode, as will be discussed furtherbelow. Indeed, scissor link or links 68, configured for verticallyextending or retracting the rotor hub/blade sets in relation to thefuselage of an aircraft, is not typically found on conventionalhelicopter for the simple reason that there is no purpose or advantagefor such an arrangement without the composite hub structure 12 and 13and the ability to change in-flight VTOL to fixed wing flight modeconfigurations, i.e., from deployed to folded or feathered rotor blades,as discussed herein. Finally, sensors 101A and 101B may be affixed tothe main drive 50 and 64 shaft gears or other location to witness thatthe two driven counter-rotating blades 14A and 16A are in verticalalignment with each other. The importance of this feature will bediscussed in more detail below in discussions of methods of in-flightVTOL to fixed wing transitions, and vice versa. In FIG. 3A, the twosensors are shown opposite each other to correspond to the position ofdriven blades 12A and 13A in the illustration, for ease ofconceptualization. Each time the two sensors pass each other on avertical plane, a signal is relayed to an instrument on the flightcontrol panel in the cockpit, to indicate the rotor RPM and moreparticularly the bearing relative to the longitudinal axis of theaircraft of the rotor driven blades 12A and 13A crossover point, sincethis relative bearing may change over time as the aircraft yaws invarious directions in a typical VTOL flight mode profile.

FIG. 3B illustrates an upper two blade rotor set consisting of a drivenblade 12A and non-driven blade 12B and a lower two blade rotor setconsisting of a driven blade 16A and non-driven blade 16B. In thisillustration and embodiment, the upper blade set rotates in a clockwisedirection and the lower blade set counter-rotates relative to the upperblade set in a clockwise direction. This provides an efficient symmetryof lift, at all times, which may be advantageous in transitioning fromone flight mode to another, according to embodiments. The fuselage ofthe hybrid aircraft is not shown in this figure since, as describedabove, the relation of the long, axis of the fuselage 8 may be pointedin any direction, even if the blades were frozen or braked to stoprotation in relation to each other at any given time. According toembodiments, the rotor blades may be of relatively stiff construction,with a thick chord tapered profile and relatively short disc span, sincethe primary purpose of the rotor blades is to provide a high liftcapacity, taking advantage of the biplane effect of counter-rotatingblades, as opposed to a compromised design that must incorporate highlift and low drag profiles in a single or unique lifting structure.Blades constructed as discussed herein may be of such high lift profilethat maximum rotor speeds may be reduced, leading to quieter flightoperations and, therefore, reduced drag and induced drag. Additionally,since a tail rotor is not required with coaxial counter-rotating rotorblade sets, noise from a tail rotor in the vortex of the main rotor discis eliminated and safety issues associated with a tail rotor flyingthrough such vortex are eliminated.

FIG. 4 illustrates a top view of a hybrid aircraft 10 with genericfuselage 8 showing two, upper and lower, coaxial, counter-rotating rotorblade sets (only the upper rotor driven portion 12A and driven blade 14Aand non-driven blade 14B are visible in this drawing) in stowedconfiguration. This stowed configuration may be achieved by applying aslight negative collective pitch to the blades to allow them to nestleleading and trailing edges in this configuration, and with theswing-wings 34A and 34B folded and stowed for aircraft stowage ortransportation purposes, according to one embodiment. In thisillustration, leading edge root extensions (LERX) 90 may be seen, asalso shown in FIG. 1 above. According to one embodiment, twin rudders 18and horizontal stabilizers 20 have been rotated such that the ruddersare near vertical and that the ends of the feathered and stowed rotorblades 14A, 14B, 16A and 16B have been captured in their stowedpositions. In this illustration, the vetically extendible rotorhub/blade sets have been lowered to their lowest position and have beenshielded by a fairing 11, as also shown in FIG. 1. Twin main gas turbineengines 26 may also be seen in this view, according to one embodiment.

FIG. 5 illustrates a top view of a hybrid aircraft 10 with rotor bladesets 14 and 16 in initial phase of deployment, according to oneembodiment. In this view, the vertical rudders 18 have rotated to theirlower position to release the previously captured rotor blade tips andthe vertically extendible rotor hubs/masts have been raised to clear thefuselage fairing 11. The direction of rotation of deployment of eachblade set, upper and lower, have been indicated by the arrows showingcounter-rotation. Deployment of the blades from or to their foldedpositions may be accomplished by the auxiliary motors discussed in FIG.3A above, according to one embodiment and method. Deployment of therotor blades from feathered or folded position may also be accomplished,for example, during flight mode transition from fixed to VTOLconfiguration, by the main engine(s) or power turbine(s), according toembodiments. In such a method, recovery of the blade sets from deployedto stowed configuration may be aided by airflow tending to fold eachblade set on itself as a result of forward flight, which may also becontrolled by rotating drive shaft brakes or the auxiliary motorsdiscussed previously, as will be discussed further below.

It may be noted that in this illustration, the non-driven blades 14Bcorresponding to the upper rotor hub and 16B of the lower rotor hub havenot yet reached the extent of their fully deployed travel within theirrespective composite hubs, as discussed in FIGS. 2A, 2B and 2C above.Only when the two driven blades 14A and 16B have met and crossed incounter-rotation will the individual blade sets be fully deployed andlocked together with the spring loaded solenoids of FIG. 2B above. Itshould also be noted that FIG. 5 may represent the blade sets fallingback to their stowed and feathered positions if the direction arrowswere reversed in this illustration. The symmetry of the counter-rotatingblade sets in relation to airflow over the aircraft during deployment orfeathering, may greatly enhance the stability of the whole hybridaircraft during in flight transitions from VTOL to fixed wing flightmodes and vice versa.

FIG. 6 illustrates a top view of a hybrid aircraft 10 showing, furtherdeployment of the blade sets 14 and 16, according to one embodiment.Such a configuration may be in preparation for a VTOL flight phaseconfiguration such as a takeoff from a carrier deck, for example. Itshould be noted that each blade set is not yet fully deployed and lockedin this view, as noted above for FIG. 5. Not visible in this view arethe horizontal stabilizers/elevators 20 of FIG. 4, since they are maskedby the lowered twin rudders 18 in this embodiment which would presentthe entire empennage of a hybrid aircraft 10 in “X” configuration ifviewed from aft looking forward, according to one embodiment. With thetwin rudders 18 in lowered position to release the rotor blades, VTOLflight safety is enhanced since the rudder profile is further out of theway of the rotor blade arc or rotor discs.

FIG. 7 is a top view of a hybrid aircraft 10 in VTOL phase of a flightmode, according to one embodiment. In this view, the individual rotorsets 14A and 14B, and 16A and 16B are in their fully raised and lockedconfiguration, as described above in previous figures, and as a resultof the two driven blades 14A and 16A having completed at least one halfrevolution and thus capturing and locking their non-driven blades intheir respective rotor hubs 12 and 13 of FIG. 3A. The twin ruddersremain in their lowered position in this flight mode, according to oneembodiment, which may uncover the side NOTAR gas vents discussed. InFIG. 1 above. The use of a NOTAR system on a coaxial counter-rotatingblade helicopter system may be advantageous in that the rotor bladespeeds may be matched to one another throughout an entire flight, sincethere would be no need to mismatch the rotor disc speeds to induce orcontrol yaw, leading to even more precise control of the aircraft inVTOL mode. A NOTAR system is not specifically needed for a coaxialcounter-rotating rotor helicopter, however, as there is no inducedtorque on the airframe because the counter-rotating torsional forces ofthe rotor discs cancel each other. A traditional means of controllingyaw on such aircraft is to vary speeds between one rotor driveshaft andanother, often requiring twin engines for that purpose alone with eachengine driving one rotor set, and therefore inducing a torquedifferential which acts on the airframe hung below the rotor blades.Such traditional aircraft induce rolling or pitching secondary effectsas a result of such a method of controlling yaw. In the presentdiscussion of a hybrid aircraft 10, bleed air from the main engines toNOTAR gas ports or even thrust vector nozzles on the main enginesthemselves may be substituted for torque differential yaw controlsystems, according to embodiments. Constantly matched rotor speedsbetween the upper and lower rotors may also aid transition from oneflight mode to another with NOTAR yaw control, particularly since it maybe desirable to transition from one flight mode to another in as stablea configuration and flight path as possible. Moreover, with NOTARsystems, there would be no need to induce an imbalance into the rotordisc sets simply to control yaw until conventional fixed wing flightsurfaces associated with the empennage could take over. It should alsobe noted that, according to one embodiment, the NOTAR system may be usedwith fixed wing flight to augment maneuverability of the aircraft duringhigh speed maneuvers.

In this figure, the upper rotor blade set turns counter-clockwise andthe lower blade set turns clockwise. According to one embodiment,forward thrust on the fuselage 8 of an aircraft 10 may be augmented oreven primarily furnished by thrust from main engines, thus increasingthe potential speed of the aircraft in VTOL mode, widening the stabletransition speed range from one mode of flight to another, and to nothave to rely on the rotor disc as the primary means for providingforward thrust. Indeed, it has been shown that in such a configuration,little power is needed to maintain rotor speed and the lift of the rotordisc, and most of the engine(s) power may be reserved for forward thruston the airframe.

FIG. 8 is a top view of a hybrid aircraft 10 with twin, coaxial,counter-rotating blade sets in folded and stowed position, and with themain swing-wings 31A and 34B in both folded, as shown by the dashedlines, and deployed positions around the main swivels 110, according toone embodiment. Small electric or hydraulic auxiliary motors may beincorporated into the fuselage structure 8 to move the wings fromdeployed to stowed configurations, according to embodiments. The left orport side deployed wing 34B illustrates features such as ailerons 114,flaps 112 and leading edge slats 116, and may also incorporate leadingedge dogtooth features, according to one embodiment. The starboard orright wing does not show these features for ease of illustration, butsuch features are assumed to exist as for the port wing. The twinrudders 18 and horizontal stabilizers/elevators 20 have been raised totheir fixed wing flight position, and locking in the distal tips of therotor blade sets, according to one embodiment discussed herein. Such afixed wing flight mode configuration may be the result of a completedtransition from VTOL mode to fixed wing mode in flight, or may be theinitial flight mode set for takeoff or landing from an adequate runwayor deck, including catapult launches. With the swing-wings stowed forVTOL flight mode, as illustrated in previous figures above, efficientrotor blade function may be realized as there is less downdraftinterference with the wing upper surfaces out of the way of the rotorblade induced air mass flow.

FIG. 9 is a top view of a hybrid aircraft 10 in a transitional phase ofa flight mode, according to one embodiment. In this illustration, eachrotor blade set consists of two rotor blades and each rotor blade set iscomposed of a driven or master rotor blade and one folding non-drivenblade, all of which are fully deployed, according to one embodiment.Since this figure illustrates a transitional phase from VTOL to fixedwing or vice versa flight modes, both the swing-wings 34A and 34B andthe coaxial, counter-rotating rotor blade sets are deployed at the sametime, such transition phase intended to be of short duration, accordingto methods. Such a transition phase may also include, for instance, aninitial fixed wing flight mode, followed by imminent or complete enginefailure, achieving best glide slope, deployment of the rotor blades bythe auxiliary electric, motors discussed under FIG. 3A above, andsubsequent swing-wing folding, also by auxiliary electric motorsdiscussed in FIG. 8 above, in preparation for an autorotation maneuverusing collective commands to set the craft down safely, according to onemethod. In this figure, the rear empennage of the aircraft shows twopotential configurations, with the twin rudders raised in preparationfor being lowered to capture the rotor blades if the transition is fromVTOL flight mode to fixed wing, flight mode or already lowered afterreleasing the rotor blades to transition from fixed wing to VTOL flightmode. It should be noted that in this instance, the arrows in thisfigure describe a relative arc of approximately 45 degrees on eitherside of the aircraft heading, and not rotor rotational direction, aswill be described in more detail in a discussion of methods below.

The well documented efficiency of coaxial counter-rotating rotor bladesets in providing a high degree of lift in relation to powerrequirements may be advantageous in transitioning from one flight modeto another, according to embodiments herein. Additionally, it should benoted that the relative symmetry of coaxial counter-rotating rotorblades may aid in the stability of the flight path, as may beadvantageous for such transitions, particularly since there is greaterstability due to gyroscopic effects in the rotor discs when rotor speedis elevated, and which diminishes as rotor speed is reduced inpreparation or initiation of transition from one flight mode to another,according to methods. Further, in this embodiment, the twin jet turbinemain engines provide energy for both forward thrust and rotor setrotation, and as has been discussed above, the ratio of powerrequirements for the rotor disc rotation, which is low, to that neededfor forward thrust is advantageous in providing a greater range ofaircraft speeds during which transition from one flight mode to anothermay be achieved.

FIG. 10 is a rear perspective view of the empennage of a simplifiedexemplary fuselage of a hybrid aircraft, according to one embodiment.This rear view sketch shows a hybrid aircraft with twin coaxial,counter-rotating blade sets deployed, swing-wings extended, and rearempennage in VTOL flight configuration, shown as dashed lines, accordingto one embodiment. In this illustration, the split rear empennage, eachhalf consisting of a rudder 18 and horizontal stabilizer with elevators20, has been lowered to free the rotor blades from their stowed andcaptured position aligned with the long axis of the fuselage. Viewedfrom the rear, the empennage now presents a flattened “X” pattern whichmoves these flight control surfaces downward in relation to the rotorblade discs, as seen under rotation, and also uncovers the high pressureair slots on each side of the rear fuselage. These air slots, with aninternal slide valve (not shown in this illustration) serve to channelhigh pressure turbine bleed air perpendicularly out of the fuselage tocontrol yaw in the VTOL configuration of the aircraft. The internalslide valves, one on each side of the fuselage, are controlled by theoutside pair of rudder pedals in the cockpit, and high pressure airdirected to one side or the other of the fuselage may turn the fuselageabout the coaxial rotor hub vertical axis. According to otherembodiments, the rear empennage may be fixed, i.e., non-rotating, androtor blade capture and stowage may be accomplished by means of flaps onthe upper fuselage, similar to those used for stowing retractablelanding gear, to lower profile and interference drag, on the airframeduring fixed wing mode flight operations. Single or dual rudders withhorizontal stabilizer/elevators or stabilators may also be found indifferent configurations, according to embodiments. In additionalembodiments, the maximum circumference of the rotor disc (bladesdeployed and rotating) or empennage profile will be such that nointerference with the empennage is possible to avoid boom strikes ormast bumping.

FIG. 11 is a top perspective view sketch of cockpit controls and layoutof a hybrid aircraft, illustrating controls for both fixed (swing) wingand VTOL configurations of the aircraft, according to one embodiment. Inthis view, a collective lever 150 with throttle may be seen to thepilots left side, and a second throttle 152 which may be slaved tothrottle 150 on the side console may also be seen. The throttle 152 maybe used in fixed wing mode to control thrust of the twin turbines as isconventionally performed. According to one embodiment, the main thrustengines may be separate from the main helicopter transmission twinturbines, and in that case the throttle for fixed wing thrust controlsthe main engine thrust, while the throttle on the collective levercontrols the helicopter turbines separately. In the case where, asdescribed in FIG. 1 above, the twin turbine main engines provide energyfor both direct thrust, for fixed wing operations, and in one embodimentvia, a gated power turbine, to drive the helicopter rotor transmission,both throttle sets control the main engines, and the master/slaverelationship between the two throttle sets are maintained, according toembodiments. In such configuration, the rotor hub drive shaft(s) mayincorporate clutches and disc brakes to allow the rotor blades to bedecoupled from the main transmission. According to one embodiment, theremay be two sets of coaxial rudder pedals 154 and 156, with the outer set154, left and right, controlling the high pressure bleed air to theNOTAR slide valves in the rear fuselage for VTOL mode of the hybridaircraft, and with the inner set 156 controlling the twin rudders in thefixed wing mode of the hybrid aircraft, allowing the pilot to easilyswitch between the two modes of controlling yaw. Both rudder setsincorporate rudder top pressure brakes for the main landing gear, andare also connected to the steerable nose wheel set. It may be envisionedthat a pilot may use both left rudders simultaneously, for example, orboth right rudders, which may then not only affect the NOTAR yaw controlbut also the rudders themselves at the same time, which may allow forincreased maneuverability combinations not found with rudders alone. Inthis manner, according to one method, increased yaw speed and slightupward pitch of the tail of the fuselage may be envisioned, as well asother combinations of flight controls that would not be possible foreither a simple helicopter or fixed wing aircraft.

Pitch and roll controls for both VTOL and fixed wing modes isaccomplished by the central stick/cyclic/joystick 158, with cycliccommands translated to the swashplates of the coaxial rotor hubs in VTOLmode and to the ailerons and elevators/canard wings in fixed wing mode,according to one embodiment. In one embodiment, both cyclic andelevator/canard wings may be linked for VTOL mode to allow for moremaneuverability options and flexibility. According to one embodiment,the leading; edges of the main swing-wings 34 may feature full length,automatic leading edge slats 116 of FIG. 8 above, and flaps may be setby the pilot by an electric switch on the central stick or joystick.Such features may allow for a greater range of speed and airframestability during which the rotor blade sets may be deployed or stowedduring transitions from fixed wing to VTOL flight modes, or vice versa.The use of leading edge slats/fuselage canards and flaps or acombination thereof may also allow for a more stable and flatter angleof attack for the swing-wings during rotor blade deployment and stowageoperations, thus allowing the counter-rotating rotor sets to deploy nearor at flat pitch for greater aircraft stability in transitions from oneflight mode to another. In one embodiment, the use of coaxialcounter-rotating rotor sets allows for intuitive flight controls in VTOLmode, with no adverse pitch tendencies in right or left turns that wouldbe associated with a single rotor disc. Because one embodiment discussedherein uses coaxial counter-rotating rotor blades, maneuvers such asflat turns, funnel maneuvers and other maneuvers such as takeoffs in anydirection regardless of relative wind direction associated with such asystem for VTOL mode are possible. Application of forward cyclic controlin VTOL mode applies increased pitch 90 degrees to starboard of thefuselage on the rotor blade set 16A and 16B, and increases pitch 90degrees to port of the fuselage on the rotor blade set 14A and 14B,lifts the rear of the fuselage resulting in a nose down pitch on theaircraft, because both rotor discs, counter-rotating to each other, actas spinning gyroscopes and the resultant force is applied approximately90 degrees in the direction of rotation of each rotor disc. As mentionedpreviously, fly-by-wire technology may simplify cyclic commands totranslate desired motion controlled by cyclic stick movement into pitchchanges on the counter-rotating rotor blades via their respective bladehubs and correspondingly into movement of the aircraft in any lateraldirection. Aircraft fuselage heading is controlled by the rudders, andcollective controls vertical movement, with combinations of all threecontrol sets resulting in complex maneuvers that only helicopters canperform.

One embodiment is a method of carrying out one or multiple in-flighttransition(s) from VTOL flight mode to fixed wing flight mode and viceversa. For discussion purposes outlining one such method, FIG. 9 may beused as one representative embodiment of a hybrid aircraft disclosedherein with swing-wings and the features illustrated thereon, twincoaxial counter-rotating two blade rotor sets, twin jet engines toprovide rotor power through a transmission as well as direct forwardthrust, a bleed air NOTAR system for VTOL mode yaw control and anempennage capable of partially rotating to assume a VTOL configurationand a fixed wing flight configuration, as discussed previously. It isassumed that either of the jet engines, operating alone, may besufficient to power the aircraft in sustained flight. Any of thefollowing flight plans, corresponding to a desired mission profile, maybe considered for examples of in-flight transition methods:

-   -   Takeoff in VTOL mode, transition to high speed fixed wing mode        for long distance leg, transition to VTOL mode and landing;    -   Takeoff in VTOL mode, transition to fixed wing mode and landing;    -   Takeoff in fixed wing mode, including a potential catapult        launch, transition to VTOL mode for a mission, landing in VTOL        mode;    -   Takeoff in fixed wing mode, transition to VTOL mode, transition        back to fixed wing mode and landing;    -   Takeoff in VTOL mode, landing in VTOL mode (no transition);    -   Takeoff in fixed wing mode, landing in fixed wing mode (no        transition); and/or    -   Other combinations involving multiple in-flight transitions from        one flight mode to another

In-flight transition methods from fixed wing to VTOL flight modes andvice versa may differ slightly with respect to methods of deploying therotor blade sets and recovering and stowing them, according toembodiments described herein. This is primarily due to the relative windforces and direction and the position relative to the fuselage of thedriven rotor blades at the moment they pass each other vertically inflight, which may vary considerably because of VTOL flight profilesinvolving changes of aircraft direction during a flight independent ofthe rotor blades turning above the fuselage.

Using FIG. 9 above as an illustration of transitional deployment of thecoaxial counter-rotating rotor blades from lowered and stowed position,such maneuvers may be relatively straightforward due to the symmetry ofthe deploying blades with respect to forward flight and the resultingairflow, and enhanced as rotor speed increases and thus the stabilizinggyroscopic effect of the rotor discs increases. The empennage is rotatedto release the blade roots and uncover the NOTAR gas ports, and the twinport and starboard rudder pedals of FIG. 11 may be used to ensure yawcontrol during the transition, according to one embodiment. The rotorhubs may be elevated clear of the fuselage fairing, the spring loadedsolenoid 46 of FIG. 2B may be activated to unlock their individual bladesets and power may be applied to the rotor transmission to startrotation, either from the auxiliary motors or main engines via a clutchmechanism, such as mentioned previously. It may be noted that since therelative wind is essentially head on and following the longitudinal axisof the aircraft in fixed wing flight that the driven rotor blades 14Aand 16A will advance into the wind symmetrically upon deployment andlocking of their respective non-driven blades will occur once the drivenrotor blades have passed one half revolution. Additionally, thenon-driven blades will always tend to feather into the relative winduntil they are locked opposite to the driven blades in the rotor hubs bythe spring loaded solenoid. Once locked, rotor blade speed may beincreased to a desired RPM value and maintained Once the rotor discshave taken over sufficient lift to transition the aircraft from fixedwing to VTOL flight mode, the swing-wings 34A and 34B may be folded totheir stored position in the fuselage. At this point, flight modetransition is completed for this instance. The transition speed rangemay vary depending on the embodiment of the hybrid aircraft, butgenerally it may be assumed that a speed range corresponding for fixedwing aircraft V_(fe) or Velocity with flaps extended to V₀ or stallspeed with flaps extended may be advantageous for flight profiletransitions. The use of flaps, canard wings, if the present aircraft isso equipped, and leading edge slats in preparation for a transitionmaneuver may serve to widen the transition speed range and also tend tolower or flatten the pitch angle of the fuselage at the lower speedsnecessary for flight mode transition, all of which may be advantageousin deploying or recovering and feathering rotor blade sets.

A transition from VTOL flight mode to fixed wing mode may involve oneadditional step to allow safe, symmetrical recovery and stowage of therotor blade sets, in VTOL mode, forward speed is brought within thetransition Speed range outlined above. The swing-wings may then bedeployed, ensuring that control surface locks have engaged for the flapsand ailerons, if necessary, flaps may be deployed to keep the aircraftitself in a relatively flattened pitch profile, and the main enginesthrust adjusted to unload the burden of lift from the main rotors. Oncewithin a satisfactory flight profile and transition speed range, therotor blades may be adjusted to flat collective pitch and power removedor reduced to the rotor blades. These latter two steps may be importantbecause they prepare the rotor hubs in anticipation of unlocking, theirdriven and non-driven blades from each other and subsequent swiveling ofthe driven and non-driven portions of both the rotor hubs and upperswashplates with their pitch links to a feathered position. Beforeunlocking the blade sets by activating the spring loaded solenoid ineach of the rotor hubs, the pitch links should already be set forneutral or flat collective pitch and the cyclic command diminished asthe pitch links will lose their effectivity as far as cyclic commandsare concerned once the hub portions are unlocked and begin to swivel tofeathered position. Collective pitch inputs will continue to beeffective, even with the rotors and upper swashplates in foldedposition. After these steps, the rotor discs are at this point acting,as essentially flat discs and lift is being transferred to theswing-wings.

It should be noted that in this first phase of the transition, thegyroscopic forces of the rotor discs will contribute to stability duringand after swing wing deployment and then gradually decrease as rotordisc speed decreases. It may additionally be advantageous to the pilotto know, in advance of this transition operation, the precise relativebearing (relative to the fuselage or aircraft current heading) to thepoint at which the driven blades 14A and 16A cross each other, and thento turn to match that with aircraft heading or be within approximately45 degrees either side of the nose to that bearing as shown by the rangeof the double headed arrows in FIG. 9 (which do not represent rotorblade rotational direction). In this manner, as the blades are unlockedand come to a stop or are braked with drive shaft brakes (not shown, butdiscussed previously) or by engagement of the electric auxiliary driveshaft motors, and the driven and non-driven blades are unlocked fromeach other, they may fold back with pressure of the relative wind toalign themselves in folded or feathered position prior to the rotor hubsbeing lowered. Note that this differs from the blade deployment methodin the previous paragraph, wherein the driven blades will automaticallybe already initially aligned with aircraft heading as they deployforward from their stowed and aligned position on the fuselage. In anycase, once the blades are unlocked in preparation for stowing, thenon-driven blades 14B and 16B will tend to feather into the relativewind and the driven blades 14A and 16A may be allowed or powered to moveback or fall back in reverse direction of their normal rotation tocomplete blade set feathering. Once the individual blade sets havereached their feathering position, the spring loaded solenoid 46 willautomatically engage and lock them in that position, as discussedpreviously. At that point, the blade sets will always want toweathervane with the rotor hubs facing the relative wind, which is astable position from which to be able to stow them properly and lockthem to the fuselage. According to embodiments herein, the empennage maybe rotated to capture the blade tips for stowage. Once the empennage israised to its fixed wing flight mode, the pilot should ensure smoothoperation of the rudder and elevators before resuming a desired coursein high speed fixed wing flight mode.

Another embodiment is a method of carrying out a safe landing of ahybrid aircraft 10 in the event of imminent or complete engine failure.In the event of imminent failure of the aircraft in fixed wing mode,such as imminent or complete engine failure, the rotor blade sets may bedeployed and used in unpowered, auto-rotation mode to allow for morelanding options for the aircraft, assuming that they can be fullydeployed and that the aircraft has sufficient altitude to achieveminimum rotor speeds in time. Auto-rotation as a means of landing, maybe used at any time in VTOL configuration or mode, as with anyconventional helicopter. Auto-rotation landing modes for the hybridaircraft, with swing-wings folded, may also be used to approach a noisesensitive landing site to set the aircraft down with minimum noise,followed by engine start or re-start at an appropriate later time forsubsequent takeoff of the aircraft in either VTOL or fixed wing mode.

According to one embodiment, a hybrid aircraft may feature twinpropulsion propeller pods or nacelles on the port and starboard side ofthe fuselage 8, and such pods may be mounted on stub wings. Each of thepropulsion pods may also supply the power for these for one of thecontra-rotating rotors overhead. With such a configuration, thestarboard pod may be linked with the rotor that is sweeping; forward onthe starboard side, and vice versa, with the port side pod. With such aconfiguration, in the event of a power outage, the remaining power plantwould automatically compensate for the increased drag on its side. Pitchchanges in the propulsion pod-propeller relative to its mated overheadrotor may enable fine tuning of offsetting torque and this couldeliminate the need tot cross-shafting while still affording twin enginesafety.

Additionally, according to another embodiment, the propulsion pods couldswivel upwards and downwards, and may in addition be configured toswivel inwards and outwards in relation to the fuselage 8. Thesefunctions ma require only limited travel to be effective, i.e., tiltingupwards during hover and transitioning to parallel the fuselage for highspeeds, but retaining their tilting options at all speeds for yawcontrol, pitch control of the whole craft, and pitch starboard relativeto port. These functions and configurations may be advantageous inmaking much more coordinated turn-and-bank maneuvers, particularly whenloading is near CG limits and where pendulum effects may be at amaximum.

According to further embodiments, these propulsion pods may be locatedon stub wings that droop in anhedral configuration for hover, and thusmay minimize downwash interference and also enhance recirculationprevention, especially for high-hot VTOL operations and when hoveringnear a pinnacle, as such operations usually present a challenge forconventional helicopters in such environments. In another configuration,i.e., fixed wing high speed flights, the stub wings and pods may beflattened or even present a slight dihedral for stability enhancement.

Additional advantages that may be found with such embodiments are thatthe pods may be slightly swiveled inwards or outwards, for instance whenin their vertical position, for slope operational stability and alsofor, again, combating recirculation problems when operating in otherchallenging environments, such as between two sheer walls, whererecirculation could otherwise prohibit lifting off at all or worse, theinevitable settling with power situation. When in their horizontalposition, they may prove advantageous for trimming purposes inhigh-speed flights if necessary, and may thus eliminate otherdrag-inducing surfaces. Such side pod thrusters may also be in the formof small turbofans, ducted units or even bleed airduct-thrust-compounding thrusters, with no moving parts other than theswiveling mechanisms if simpicity is desirable, and according to furtherembodiments.

According to another embodiment, the individual rotor blades connectedto a composite hub 12 or 13 may be constructed of two or moretelescoping, components that may present certain advantages forin-flight transition from VTOL to fixed wing aircraft flight modes, aseven as little as the addition of one telescoping section may provide alarge advantage in the process of transition of load to the swing-wings,as well as for rotor blade slowing and stowing phases. With such anembodiment, in addition to allowing more compact storage areas on thefuselage or wings for the rotor blades, the rotor blade folding andstowage process could take advantage of conservation of energy and couldhelp offset the huge gyroscopic forces associated with the rotorinertia, as well as the inertia component itself in each rotor blade,while perhaps significantly reducing aerodynamic loads during theoverlapping process where the blades are potentially unbalanced for eachrotor head. The in-flight mode transition may thus includetelescoping/collapsing the rotor blades as the lift load, is transferredto the wings—such reduction in diameter would naturally increase rotorrpm but riot necessarily beyond supersonic tip speeds given thereduction in tip travel distance. A subsequent step may be to slow therotor speed down and then allow the driven rotors to stop in full aftposition relative to the fuselage 8, allowing the non-driven rotors tocatch up and also stop aft, followed by the fairing 11 raising andfolding to cover them similar to the way a main gear door folds to closeover a wheel well opening for retractable landing gear. In that way, theengines, rotor heads and rotor shafts may all be stationary with thelightweight cover doors doing the moving for stowage purposes.Transition to slow speed VTOL mode while re-loading the rotors to takethe bulk of the lifting forces may be a reverse procedure to the abovefor collapsing and stowing the rotor blades. The forces for telescopingthe rotor sections may either be in the form of an internal band whichmay pull the outboard rotor section(s) towards the rotor hub portion towhich the rotor blade is connected, or alternatively by the use ofdriving gas pressure to the overlap space between telescopic sections,which when expanded, will tend to collapse or telescope the rotor bladesinwards to a reduced diameter for lift load transition between flightmodes and for rotor blade stowage. According to still furtherembodiments, such telescoping rotor blades may be captured by extendingthe upper fuselage of FIG. 1 forward and then stopping the bladesparallel to such an extended upper-fuselage fairing fore and aft,followed by stowing the rotor blades in unfolded configuration, with orwithout telescoping them first as part of the rotor blade stowageprocess.

According to one embodiment, the swing-wings 34 may be configured tosweep forward, and in combination with coaxial counter-rotating rotorswith three blades per rotor, such wings may be swung out forward inrelation to the fuselage 8 to meet up with four of the six rotor blades(three mounted on each of the coax rotor heads). The first phase of anin-flight transition from VTOL to fixed wing flight mode may beswinging, the port and starboard wings 34 forward to unload the rotorblades, followed by raising the wings up to nest four of the six rotorblades with the remaining two stowed in the aft fuselage fairing.

According to another embodiment, assuming three-bladed counter-rotating,coaxial rotor pairs, the rotors fur both sets could be halted inposition where the aft rotor of each pair of counter-rotating, coaxialrotor sets is aligned with the fuselage (and airflow while in high speedforward flight) while the two remaining rotors are then swiveled back toan optimal sweep back position to act as stable, fixed airfoils toaugment fixed-wing lift or to stand-alone as the main lifting surfacesduring high speed flight. In this case, the leading edges of the halted,now optimally swept airfoils nee rotor blades remain leading edgesduring fixed configuration for high-speed flights. In thisconfiguration, they may be swiveled at their roots a la “full-flying”operation and optionally, advantageously retaining the control elementsused for cyclic and collective functioning while in rotation to changethe pitch for fixed mode control. Alternatively, they may also havesurfaces such as flaps, ailerons and flaperons for control.

According to further embodiments, following on the above, the rotorsthat are stopped and optimally swept could also be hinged at a distancefrom their roots, such that they may be of shorter, stiffer chord, withthe outboard sections either hinged all the way to contact, nest or nearcontact with the root sections or they may be hinged to the point wherethey make contact with the fuselage forming a rigid, high-strength “A”section together with the fuselage on each side. Any negative impact ofthe fact that trailing edges are now leading edges on (only) thetrailing portions of the “A” sections may be minimized by theircross-section, which tends to be flatter and often symmetrical or nearlyso, in many existing rotorcraft designs already. In any case, theseflatter sections could be independently movable to act as pitch controlsas well, with or without root section mobility.

According to another embodiment, the swing-wings 34 may be swiveledvertically instead of swinging to stow within the fuselage 8 or deployoutside of the fuselage. This may allow the rotors to be stowed in suchswing-wings and may even be configured to complete the upper surfaces ofwings that are fixed out each side of the fuselage. Such verticallyswiveling wings may thus angle upwards in pitch during hover and levelout as forward flight speed is increased, thus minimizing interferencewith rotor wash during hover and other VTOL flight operations.

According to still further embodiments, the wings of a hybrid aircraft10 may present a horizontal X-configuration, which may have both forwardsweep and back sweep fixed or swing-wings at for example 45-degreeangles upon which the 4-rotor blade configuration illustrated in variousfigures above may be stowed without a need for rotor hub/blade foldingprior to flight mode transition from VTOL to fixed wing flight modes.Such wings may also be configured to pitch to vertical for hover/VTOLmode and could also incorporate the landing gear at the tips in largewinglets that droop in relation to the ground, and then swivel tohorizontal for transition to high speed flight with the droopingwinglets now being configured as effective winglets for efficiency,according to one embodiment.

According to one embodiment the hybrid aircraft 10 may be configuredwith Anton Flettner intermeshing but composite rotors in place ofcoaxial counter-rotating rotors as previously described herein. Suchintermeshing rotors must of necessity be in constant synchronicity witheach other in relation to their individual rotation, and thus a methodfor feathering/stowing the driven and non-driven rotor blades may beaccomplished in the same manner as previously described above.Additionally, according to embodiments, such intermeshing rotors may beconfigured to be side-by-side in relation to the fuselage or fore andaft of each other, along the longitudinal axis of the fuselage of ahybrid aircraft 10. In the latter configuration loading and unloading ofpassengers could happen at the sides instead of at the front and rear,as in usual intermeshing rotorcraft, and may also enable stowing of therotor blades to be a relatively simple and streamlined operation.According to one embodiment, wherein the intermeshing rotor hubs areside by side in configuration, a vertical X-wing swing-wing pattern,(presenting a fiat and subsequently an “X” shape when viewed from therear of the fuselage, for example) may also be incorporated into thefuselage of a hybrid aircraft 10. In such embodiment, the inboard rotorwould store in the opposite side upper X-wing and the outboard rotorblade would stow in the same side (lower X-wing) and vice versa, giventhat intermeshing rotors outboard rotor blades are typically configuredto be slanting ground-wards and the inboard intermeshing, rotor bladestilt towards the sky. There would be a need to completely stop theblades from rotating prior to splitting the wings into their upper andlower X-con figuration in such an embodiment.

According to embodiments, an individual rotor blade may be asymmetricalin length on either side of the rotor hub to which it is affixed or inrelation to other rotor blades on the same hub, for instance for a givenrotor hub to have two short and one long blades or one short fat/wideblade and one long thin one on the same hub, which may be advantageousin simplifying folding from an aerodynamic standpoint, and wherein afirst phase may be to stop the long blade in aft position relative tothe fuselage 8 of a hybrid aircraft 10, then fold the one or two shortstub rotors aft in a next phase followed by stowage of the folded bladesas described by one of the methods previously. According to furtherembodiments, rotor blades may also present features such as dog toothtips, leading edge slats, winglets or other features. In one embodiment,the addition of small winglets at the tips of the rotor blades thatcould swivel to align with rotational flows in hover and then wouldgradually be swiveled to progressive positions to force the rotors toslow and finally stop once aligned in the desired position(s) with thefairing(s) may be advantageous. Such a configuration could significantlylessen the need for heavy slowing equipment like brakes and shockabsorbing equipment to slow the rotor blades m anticipation for folding,and stowing operations. Also, such a configuration could include smallrollers near the rotor tips and corresponding ramps in case therehappens to be a lot of turbulence that might otherwise damage the tipsin transition to stowage. Alternative the rollers could be located inthe stowage area on the fuselage or wings rather than at the rotor tips,in which case the tips of the rotors could contact the soft rollers onceclose to such stowage area(s).

It is to be understood that any of the method descriptions herein arebut exemplary methodologies and that one or more of the steps describedabove may be omitted, while other steps may be added thereto to any ofthese embodiments, depending on the mission configuration intended forspecific embodiments. Other operator method embodiments and deviceembodiments are supported as well. The order of some of the stepsdescribed herein may additionally be changed, according, to any desiredprocedure or mode of operation,

It is also to be understood that any dimensions or descriptions referredto or illustrated herein are exemplary in nature only Those of skill inthis art will recognize that other dimensions and/or configurations maybe implemented, depending upon the application, and that the elements ofthe device could be of any length or dimension, all of which areconsidered within the scope of this disclosure. Furthermore, anydiscussion of dimensions or ranges of dimensions or physical or dynamicaspects such as flow rates or ranges of motion or time factors orembodiment configurations outlined herein are exemplary in nature onlyand should not be considered to be limiting.

While certain embodiments of the disclosure have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novelmethods, devices and systems described herein may be embodied in avariety of other forms and other applications. All such otherapplications making use of the principles disclosed herein for thisdevice and that could be envisioned by one skilled in the art aretherefore considered to be within the scope of this disclosure.Furthermore, various omissions, substitutions and changes in the form ofthe methods and systems described herein may be made without departingfrom the spirit of the disclosure. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of the disclosure. For example, thoseskilled in the art will appreciate that in various embodiments, theactual physical and logical structures and dimensions thereof may differfrom those shown in the figures. Depending on the embodiment, certainsteps described in the examples above may be removed while others may beadded. Also, the features and attributes of the specific embodimentsdisclosed above may be combined in different ways to form additionalembodiments, all of which fall within the scope of the presentdisclosure. Although the present disclosure provides certain embodimentsand applications, other embodiments that are apparent to those ofordinary skill in the art, including embodiments which do not provideall of the features and advantages set forth herein, are also within thescope of this disclosure. Accordingly, the scope of the presentdisclosure is intended to be defined only by reference to the appendedclaims.

What is claimed is:
 1. An aircraft, comprising: a fuselage;counter-rotating and co-axially disposed first and second rotor hubs,each coupled to the fuselage and each comprising a driven portioncoupled to a driven blade and a non-driven portion coupled to at leastone non-driven blade, the driven blades and the non-driven blades beingconfigured to selectively assume a deployed configuration in which theyare configured to provide lift for the aircraft and a stowedconfiguration in which the driven blades and the non-driven blades atleast partially overlap each other and do not provide substantial liftfor the aircraft; and at least one wing coupled to the fuselage,configured to provide lift for the aircraft at least when the drivenblades and non-driven blades are in the stowed configuration, whereinthe driven and non-driven blades are selectively configured to assume,at least during sustained flight of the aircraft, the deployedconfiguration and the stowed configuration.
 2. The aircraft of claim 1,wherein the non-driven blade is configured for free rotation untilentrained in rotation by the driven portion.
 3. The aircraft of claim 1,further comprising at least one locking mechanism configured toselectively lock the driven and non-driven blades in the deployedconfiguration and in the stowed configuration.
 4. The aircraft of claim1, further comprising an upper swashplate coupled to the driven portionand to the non-driven portion and configured to selectively assumedeployed and stowed configurations and to cause the driven andnon-driven blades to change their pitch.
 5. The aircraft of claim 4,wherein the upper swashplate comprises a first portion coupled to thedriven portion and a second portion coupled to the non-driven portion.6. The aircraft of claim 5, further comprising a first lever armconnecting, the first portion and the driven portion and a second leverarm connecting the second portion and the non-driven portion.
 7. Theaircraft of claim 4, further comprising a lower swashplate that isresponsive to collective and pitch controls and that is coupled to andcontrols the upper swashplate.
 8. The aircraft of claim 1, wherein thenon-driven portion is concentrically disposed within the driven portion.9. The aircraft of claim 1, wherein each of the at least one wing isconfigured as a fixed wing.
 10. The aircraft of claim 1, wherein each ofthe at least one wing is movable to assume at least a firstconfiguration and a second configuration.
 11. The aircraft of claim 1wherein, in the stowed configuration, the driven and non driven bladesare stowed at least partially within the fuselage.
 12. A method,comprising: providing an aircraft comprising counter-rotating andco-axially-disposed blades and at least one wing; rotating the blades;flying the aircraft in a first configuration in which the rotatingblades provide most of the lift to enable the aircraft to take off or tosupport the aircraft in sustained flight; during sustained flight,causing the blades to cease rotation and to at least partially overlapeach other; continuing to fly the aircraft in a second configuration inwhich the at least one wing provides most of the lift to support theaircraft in sustained flight.
 13. The method of claim 12, furthercomprising stowing the at least partially overlapped blades duringflight of the aircraft.
 14. The method of claim 12, wherein causingcomprises deploying the at least one wing from a first wingconfiguration to a second wing configuration.
 15. A method, comprising:providing an aircraft comprising counter-rotating andco-axially-disposed blades and at least one wing; flying the aircraft ina first configuration in which the at least one wing provides most orall of the lift necessary to support the aircraft in stable flight andin which the blades at least partially overlap and do not providesubstantial lift; during flight, reconfiguring the aircraft in a secondconfiguration in which the blades are configured to provide most or allof the lift necessary to maintain the aircraft in sustained flight. 16.The method of claim 15, further comprising taking off with the aircraftin the first configuration.
 17. The method of claim 15, furthercomprising taking off with the aircraft in the second configuration and,during flight, reconfiguring the aircraft to the first configuration.18. The method of claim 15, further comprising reconfiguring the atleast one wing from a first wing, configuration to a second wingconfiguration at least during or after reconfiguring the aircraft in thesecond configuration.